My goals for this year is nothing but strength.
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[1] Do I suck it up and keep at SS, eat more food to facilitate any bit of gains? Or do I switch things up?
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[2] Have I sucked up all the gains I'm going to make on SS regardless of the weights I'm lifting and my body weight? It's been nearly 8 months...

1. Switch things up.
2. Probably. It was a good long run, I'd say.

I'll be a bit more specific with what I think are your options, since your first sentence is "this year is nothing but strength", and I'll make it easy.

Personal Favorite choice: Wendler's 5/3/1. Do one major lift a day, rotating intensity, then whatever assistance work or conditioning fits your goals. This is probably the most flexible and comprehensive program for strength I know of...

If you just want to be kinda lazy, but get stronger weekly, but very powerlifting specific: Pavel's 80/20 Powerlifting routine.

If you don't mind spending a lot of time in the gym three times a week, Texas Method or Bill Starr's 5x5 are good.

That's about it, I really like the 5/3/1 method, very flexible and fun, set PRs in lots of rep ranges, cycling intensity, and the important part of the workouts are planned out specifically in detail for you, and the unimportant parts are left up to you to do what you want to. Buy the book from elitefts if you want to try it out